In a typical X-ray photon radiation examination, a source projecting X-ray radiation is focussed at a subject to be examined and the radiation is either absorbed by the subject or travels through the subject. Some of the radiation which passes through the subject travels unimpeded directly along the path at which it was emitted from the source while some of the radiation which passes through the subject is scattered by the subject at an angle and along a path which is different from the path at which the radiation was travelling upon its original projection from the source. The object in a typical X-ray irradiation examination cycle is to detect and record as much of the unscattered radiation which passes through the subject as possible thereby providing as true a shadow image of the subject as possible. It is therefore desirable to filter out as much of the scattered radiation as possible before it reaches the X-ray photon sensitive detector because the detection of such scattered radiation will distort the trueness of the shadow image.
Providing a grid apparatus comprising a series of X-ray photon absorptive strips in close proximity to the X-ray photon sensitive detector screen provides a mechanism for filtering some of the radiation which is scattered by the subject. Prior grid systems, however, do not align the strips such that the strips are focussed at the X-ray photon source which results in the grid apparatus filtering (absorbing) critical unscattered radiation in addition to unwanted scattered radiation.
The present invention relates to a focussable grid apparatus, and in particular to a grid apparatus which is variably and adjustably focussable to a wide variety of focal lengths.
It is therefore an object of the invention to provide a focussed and a variably focussable X-ray photon absorptive grid apparatus.